Re: [PATCH] Update qemu-kvm to allow a larger BIOS image.

[Sheng Yang <sheng@linux.intel.com>]

On Thursday 16 July 2009 08:12:15 Jordan Justen wrote:
> Previously the KVM kernel module would allocate the address range
> of 0xfffbc000-0xfffbcfff for the EPT Indentity Page Tables.
> A separate patch is moving that to 0xfeffc000-0xfeffcfff.

Hi Jordan

You need one more patch for upstream kvm, to include the modification of 
vmx.h.
>
> This patch updates qemu-kvm to move the VMX TSS Pages & update the
> KVM BIOS code to update the E820 BIOS call memory reservations.
>
> Previously, the VMC TSS Pages were located at 0xfffbd000-0xfffbffff.
> This change moved them to 0xfeffd000-0xfeffffff.
>
> This change also updates the KVM bios such that the E820 locations
> are returned properly for these two changes.
>
> From a high level, these are the effects of these two changes:
>
> Previously, the KVM would only accommodate a 256KB BIOS image.  With
> these changes, the BIOS image may now grow to 16MB.
>
> Motivation for making these changes:
>
> A larger firmware image size allows alternative BIOS images to be
> used with KVM.  Some possible uses are to enable UEFI firmware
> or coreboot firmware.  Additionally, an alternative firmware might
> include a linux kernel+initrd payload, which would require several
> megabytes.

I think if you update bios to UEFI, the E820 should be represented by UEFI 
rather than current bios?

-- 
regards
Yang, Sheng

> Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
> ---
>  kvm/bios/rombios.c        |    8 ++++----
>  kvm/include/x86/asm/vmx.h |    2 +-
>  qemu-kvm-x86.c            |    2 +-
>  3 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/kvm/bios/rombios.c b/kvm/bios/rombios.c
> index 6186199..2d0c153 100644
> --- a/kvm/bios/rombios.c
> +++ b/kvm/bios/rombios.c
> @@ -4596,14 +4596,14 @@ ASM_END
>                      case 5:
>                          /* 4 pages before the bios, 3 pages for vmx tss
> pages, * the other page for EPT real mode pagetable */
> -                        set_e820_range(ES, regs.u.r16.di, 0xfffbc000L,
> -                                       0xfffc0000L, 0, 0, 2);
> +                        set_e820_range(ES, regs.u.r16.di, 0xfeffc000L,
> +                                       0xff000000L, 0, 0, 2);
>                          regs.u.r32.ebx = 6;
>                          break;
>                      case 6:
> -                        /* 256KB BIOS area at the end of 4 GB */
> +                        /* 16MB BIOS area at the end of 4 GB */
>                          set_e820_range(ES, regs.u.r16.di,
> -                                       0xfffc0000L, 0x00000000L ,0, 0, 2);
> +                                       0xff000000L, 0x00000000L ,0, 0, 2);
>                          if (extra_highbits_memory_size ||
> extra_lowbits_memory_size) regs.u.r32.ebx = 7;
>                          else
> diff --git a/kvm/include/x86/asm/vmx.h b/kvm/include/x86/asm/vmx.h
> index df8d4f9..99e2bb9 100644
> --- a/kvm/include/x86/asm/vmx.h
> +++ b/kvm/include/x86/asm/vmx.h
> @@ -403,7 +403,7 @@ enum vmcs_field {
>  #define VMX_EPT_EXECUTABLE_MASK			0x4ull
>  #define VMX_EPT_IGMT_BIT    			(1ull << 6)
>
> -#define VMX_EPT_IDENTITY_PAGETABLE_ADDR		0xfffbc000ul
> +#define VMX_EPT_IDENTITY_PAGETABLE_ADDR		0xfeffc000ul
>
>
>  #define ASM_VMX_VMCLEAR_RAX       ".byte 0x66, 0x0f, 0xc7, 0x30"
> diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
> index daf60b6..b5306aa 100644
> --- a/qemu-kvm-x86.c
> +++ b/qemu-kvm-x86.c
> @@ -63,7 +63,7 @@ static int kvm_init_tss(kvm_context_t kvm)
>  		 * this address is 3 pages before the bios, and the bios should present
>  		 * as unavaible memory
>  		 */
> -		r = kvm_set_tss_addr(kvm, 0xfffbd000);
> +		r = kvm_set_tss_addr(kvm, 0xfeffd000);
>  		if (r < 0) {
>  			fprintf(stderr, "kvm_init_tss: unable to set tss addr\n");
>  			return r;